1. Field of the Invention
The instant invention is directed to a new process for manufacturing pesticidally active materials as well as the intermediates thereof. More particularly, the instant invention is directed to a process for manufacturing 1-aryl substituted pyrazoles.
2. Background Art
Many manufacturing processes have been described in the literature for preparing such derivatives, for example in International Patent Publication Nos. WO87/03781, WO93/06089 and WO94/21606; in European Patent Publication Nos. 0295117, 0403300, 0385809 and 0679650; U.S. Pat. Nos. 5,232,940 and 5,236,938; and German Published Patent Application No. 19511269.
The Japp-Klingemann reaction, reviewed in Org. React., Vol. 10, pages 143-178 (1959), known in the literature since 1887, is a process by which phenyl azo compounds are formed from the reaction of diazonium salts with active methylene compounds. Typically the phenyl azo compound is not isolated, but is reacted in situ with base resulting in loss of a leaving group and formation of the corresponding hydrazone. When the phenyl azo intermediate is properly substituted, a spontaneous cyclization reaction occurs giving a 3,5-disubstituted-4-protio-pyrazole, that is, a 3,5-disubstituted-4-unsubstituted pyrazole. If a 3,4,5-trisubstituted pyrazole is desired, further manipulation is required in subsequent steps.